WPF 循环显示列表

<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition Height="{Binding RelativeSource={RelativeSource AncestorType=local:ScrollList},Path=ItemHeight}"/>
<RowDefinition/>
</Grid.RowDefinitions>
<ScrollViewer x:Name="tt" Grid.RowSpan="3" PreviewMouseWheel="tt_PreviewMouseWheel"  ScrollViewer.VerticalScrollBarVisibility="Hidden" >
<StackPanel x:Name="stacktt"  Background="Gray">
</StackPanel>
</ScrollViewer>

<Rectangle Height="1" Fill="Red" Grid.Row="1" VerticalAlignment="Top"/>
<Rectangle Height="1" Fill="Red" Grid.Row="1" VerticalAlignment="Bottom"/>
</Grid>

public partial class ScrollList : UserControl
{
public ScrollList()
{
InitializeComponent();
this.Loaded += ScrollList_Loaded;
}

private void ScrollList_Loaded(object sender, RoutedEventArgs e)
{
stacktt.Children.Clear();
for (int index = 0; index < ShowItemCount; index++)
{
TextBlock text = new TextBlock() { Height=ItemHeight};
stacktt.Children.Add(text);
}
RefreshData();
}

public List<int> DataSource
{
get { return (List<int>)GetValue(DataSourceProperty); }
set { SetValue(DataSourceProperty, value); }
}

// Using a DependencyProperty as the backing store for DataSource.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty DataSourceProperty =
DependencyProperty.Register("DataSource", typeof(List<int>), typeof(ScrollList), new PropertyMetadata(new List<int>()));

public int SelectData
{
get { return (int)GetValue(SelectDataProperty); }
set { SetValue(SelectDataProperty, value); }
}

// Using a DependencyProperty as the backing store for SelectData.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectDataProperty =
DependencyProperty.Register("SelectData", typeof(int), typeof(ScrollList), new PropertyMetadata(0));

public int ItemHeight
{
get { return (int)GetValue(ItemHeightProperty); }
set { SetValue(ItemHeightProperty, value); }
}

// Using a DependencyProperty as the backing store for ItemHeight.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty ItemHeightProperty =
DependencyProperty.Register("ItemHeight", typeof(int), typeof(ScrollList), new PropertyMetadata(20));

int ShowItemCount { get {
return (int)ActualHeight / ItemHeight;
} }

int startIndex = 0;

private void tt_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
{
Console.WriteLine("TimeStap={0} Delta={1}", e.Timestamp, e.Delta);

if (DataSource.Count == 0)
return;

if (e.Delta > 0)
{
if ((startIndex + ShowItemCount) < DataSource.Count)
{
startIndex += 1;
}
else
{
startIndex = 0;
}
}
else
{
if ((startIndex - ShowItemCount) < 0)
{
startIndex = DataSource.Count - 1;
}
else
{
startIndex -= 1;
}

}

RefreshData();

}

private void RefreshData()
{
if (DataSource.Count > 0)
{
int count = 0;
foreach (var item in stacktt.Children)
{
if ((startIndex + count) > (DataSource.Count - 1))
{
(item as TextBlock).Text = DataSource[startIndex + count - DataSource.Count].ToString();
}
else
{
(item as TextBlock).Text = DataSource[startIndex + count].ToString();
}
count += 1;
}
TextBlock selectText = (TextBlock)VisualTreeHelper.GetChild(stacktt, ShowItemCount / 2);

if (ShowItemCount%2 != 0)
{
selectText = (TextBlock)VisualTreeHelper.GetChild(stacktt, ShowItemCount / 2+1);
}
SelectData = Convert.ToInt32(selectText.Text);

}
}

}